1. Field of the Invention
The present invention concerns a micro-cantilever as a driving portion of an MEMS device (microelectromechanical coupling device) such as a micro-switch or a micro-actuator.
2. Description of the Related Technology
Various electronic equipments used in high frequency bands, for example, mobile telephones or wireless equipments have been decreased in the size and the weight and improved in the performance. Correspondingly, micro-switches utilizing the MEMS technique instead of semiconductor switches such as FET (field effect transistor) or PIN diodes used for controlling signals in existent electronic equipments have been proposed. Such MEMS devices can add, to electric circuits, a feature that can be difficult to attain by the electric circuit alone. For example, by replacing mechanical relays, FET, and PIN diodes used as switching devices for electric circuits with MEMS switches, it can be expected for the improvement of characteristics that have been dependent on materials such as decrease of isolation or insertion loss in high frequency regions of 10 GHz or more, or widening of frequency regions to be used. Further, since the MEMS device has a good matching property with production processes for semiconductor devices, hybrid devices integrated with thin film capacitors or thin film inductances can also be attained.
In recent years, a problem has been increased for the battery driving time along with decrease in the size and improvement for the function in mobile telephones, wireless equipments or the like. Therefore, a demand for decreasing the consumption power and low voltage driving has been increased. The MEMS technique involves several driving systems such as electrostatic, electromagnetic, and thermal driving systems. Among them, thermal driving or electromagnetic driving increases consumption power by a supply of current. Further, the electrostatic driving consumes less power since the current is not supplied but generally requires a voltage as high as 20 to 50 V. In view of the above, a piezoelectric substrate has been noted as a system capable of making less consumption power and low voltage driving compatible and an MEMS switch using the same has been proposed, for example, in JP-A-2005-332802, and the like.
The MEMS device using such a piezoelectric substrate includes those having a micro-cantilever for a driving portion. The micro-cantilever has a structure of bonding a plate-like piezoelectric substrate formed with electrodes on both surfaces thereof and a plate-like resilient member such as made of a metal or metal oxide and is supported in a cantilever manner on a support such as a substrate. In such a structure, the piezoelectric substrate displaces by the application of a voltage to electrodes to bend a micro-cantilever and it returns to an original state by the resiliency of the resilient member upon interruption of current supply to the electrodes. By utilizing the action described above, it is possible to form a micro-switch by disposing an electric contact at the top end of the micro-cantilever or form a micro-actuator having a micro-cantilever as a driving portion conducting vibrating or swinging movement.